Quick Answer
None of the three matters most on its own. RTP and house edge are the same number viewed from opposite sides - a 96% RTP means a 4% house edge, always adding up to 100% - while volatility is a separate concept describing how a game pays, not how much. For a fixed bankroll over a long session, prioritize high RTP (low house edge) and low-to-medium volatility; if you're chasing a single big win and can afford to lose your stake, volatility matters more than either.
RTP, volatility, and house edge get thrown around interchangeably in casino guides, but they're not interchangeable at all - two of them are actually the same number, and the third measures something completely different. Here's what each one actually tells you, and which to prioritize depending on how you play.
RTP and House Edge Are the Same Number, Just Flipped
Return to Player (RTP) is the percentage of all money wagered on a game that's paid back to players over the long run - a 96% RTP means a slot theoretically returns $96 for every $100 wagered, given enough spins. House edge is simply what's left over: 100% minus RTP. A 96% RTP and a 4% house edge describe the exact same game the exact same way, just from opposite sides of the counter. Casinos tend to advertise RTP because the bigger number reads better; either way, there's no additional information hiding in one figure that isn't already in the other.
Volatility Measures Something RTP Can't
Volatility (sometimes called variance) describes the shape of a game's payouts, not their size on average. Two slots can share an identical 96% RTP and still feel completely different to play: a low-volatility game pays that 96% back in frequent, modest wins that keep your balance relatively stable, while a high-volatility game pays the same 96% back in long dry stretches punctuated by occasional large hits. Neither structure is "better" in the RTP sense - they're mathematically equivalent over enough spins - but they produce very different short-session experiences with the exact same long-run math underneath.
House Edge by Game: Where the Numbers Actually Differ
House edge varies far more by game choice than most players realize. Blackjack played with correct basic strategy runs under 1%. European roulette sits at 2.7%, while the American double-zero wheel runs closer to 5.26% - nearly double, for what looks like the same game. Baccarat's banker bet runs about 1.06%, edging out the player bet at 1.24%, while the tie bet's house edge climbs well into double digits despite the tempting payout. Slots vary the most of all, typically 2-10% depending on the specific machine, since unlike table games there's no universal "slots number" - each title sets its own RTP individually. For the full per-game breakdown and how to actually play each one to minimize the house edge, see our guide on what actually improves your odds.
Which Actually Matters Most for How You Play?
It depends entirely on your session, not on some universal ranking of the three. Playing a long session on a fixed budget, purely for entertainment? Prioritize high RTP and low-to-medium volatility, so your bankroll lasts and the session stays enjoyable rather than swinging wildly. Chasing a single big win and comfortable losing your stake trying? Volatility matters more than RTP at that point, since you're optimizing for the size of a rare outcome, not the average. Playing table games specifically? House edge deserves the most attention of the three, because correct strategy directly changes it in blackjack and video poker in a way nothing changes a slot's fixed RTP.
Where to Find These Numbers Before You Play
Reputable online casinos publish RTP and volatility directly in a slot's info screen or paytable, typically behind an "i" icon before you spin - and increasingly display both openly as players ask for more transparency. Treat their absence as a real signal: a slot or casino that won't state its RTP anywhere is withholding exactly the number that tells you what you're actually playing for.
None of these three numbers wins on its own - a high RTP doesn't protect you from a volatile game draining your session early, and a low house edge on a table game means nothing if you're not playing correct strategy. Read them together, match the combination to how you actually want to play, and you'll make sharper choices than most players who fixate on whichever single number happens to be advertised loudest.